Magnetron tuner device



y 1957 c. v. LITTON 2,799,802

MAGNETRON TUNER DEVICE Filed April 16, 1954 I FIG. I.

FiGQ 3.

FIG. 2.

lNVENTOR C. 1 ITTO/V ATTORNEY i ed States Patent G MAGNETRON TUNER DEVICE Charles V. Litton, Redwood City, Calif., assignor to Litton Industries, Inc.

Application April 16, 1954, Serial No. 423,705

Claims. (Cl. 31539.61)

This invention relates to tunable magnetrons and more specifically to magnetrons wherein multi-cavity operating units are used to adjust the tuning of the magnetrons.

It is recognised that, in the construction of tunable magnetrons, certain limitations exist with respect to the obtaining of maximum output energy when the tuning of the magnetron is effected over a considerable range. In the present multi-resonator magnetrons the magnetic pole pieces are brought as close to the vanes forming the resonators as is practicable. The pole pieces are generally shaped so as to present a high concentration of magnetic flux adjacent the cathode. The pole pieces themselves are generally of magnetic steel and in order to reduce the losses are covered with copper. In building magnetrons operating in the upper frequency ranges, the effective cavity formed by the slanting pole piece face, together with the outer wall of the magnetron and the upper surface of the vanes, tend to approach the resonant frequency produced in the magnetron cavities. In order, therefore, to avoid the effects of such extraneous resonators it is the practice in constructing those portions of the magnetron envelope, outside the resonator assembly, known as the pill box, to use a copper filling intermediate the ends of the pole piece, adjacent the cathode, and the walls of the magnetron thus producing a substantially parallel plane surface spaced from the upper and lower edges of the magnetron vanes.

This pill box arrangement is preferably dimensioned so that it is small enough to approximately, but not exactly, be resonant with the fundamental frequency in a disc mode. If the pill box is too large there may be developed harmonic resonance in relation to the pill box size and some of these harmonics may be resonant at the magnetron operating frequency. However, the spacing provided by the pill box cavity does serve to produce an intercoupling among the resonators so that control of the oscillations is properly effected.

In producing fixed tuned magnetrons, in the so called X band, spacings of .050 inch between the surface of this conductive covering and the edges of the vanes have been used. This spacing itself represents a certain loss of energy due to the impedance effects, but very high efiiciencies may be obtained when fixed tuned magnetrons are produced. However, the introduction of tuning plungers into the cavities radially or axially tends to increase attenuation losses so that output energy from the magnetrons is not uniform over the entire frequency spectrum through which the magnetron can be tuned.

In a previously proposed construction described in my patent application Serial No. 368,037, filed July 15, 1953, an arrangement is proposed which, in part, avoids the losses which are created when plungers are used. This construction utilizes a rotatable disc which introduces an impedance variation uniformly into all of the resonators. However, an arrangement such as shown in this application provides a limited tuning range since the introduced tuning sections are primarily in the inductive end of the resonators and, therefore, cannot extend the range by pre- 2,799,802 Patented July 16, 1957 dominately capacitive tuning at the other end of the range.

According to the present invention tuning is effected by a rotatably adjustable tuning means which may occupy, in part, the normal end spacing provided in the magnetron pill box. Thus, in effect, the tuning is accomplished by utilizing the impedance effect of this normally present pill box cavity. At the same time, the tuning element is so constructed that it may provide a capacitive tuning to extend the tuning range of the resonators at one end and an inductive tuning effect to extend the range of the tuning at the other end of the operating frequency range.

The above-mentioned and other features and objects of this invention and the manner of attaining them will become more apparent and the invention itself will be best understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, in which:

Fig. 1 illustrates an axial cross sectional view of a por tion of a magnetron embodying the features of this invention.

Fig. 2 represents a cross sectional feature taken along the line 22 of Fig. l and Fig. 3 is a sectional view illustrating a modified type of tuner arrangement.

Referring to Figs. 1 and 2, an example of a magnetron incorporating the features of my invention is described.

The magnetron may include the usually emitting cathode 1, anode body ring 2 and radial vanes 3 which, together, form the resonator cavities of the anode. For the purpose of maintaining proper mode of oscillation strapping rings may be provided as indicated at 4, these rings being arranged intermediate the edges of the vanes for reasons which will be more clearly understood as the description of the invention proceeds. Pole piece elements 5 may be mounted inside a copper covering 6 so as to space the end of the pole piece closely adjacent to cathode 1. Fastened to pole pieces 5 are provided copper elements 7. These serve to fill in the normal cavity that would be present otherwise and so reduce the danger of developing unwarranted resonance close to the operating frequency. These copper elements 7 have formed in their surface facing vanes 3, openings which at their maximum height are equal to substantially the normal spacing that would be provided in a fixed tuned magnetron. Other portions 8, 9 and 10 of elements 7 are spaced closely adjacent the edges of the vanes. The general form and shape of the elements 7 and the openings therein can be readily understood by reference to Figs. 1 and 2 of the drawing. It will thus be seen that there are effectively provided in the surface of elements 7 a series of openings or depressions 8. These depressions are efiectively de fined by series of protrusions extending radially toward the center of the magnetron as indicated at 9 in Fig. 2. On the inner radial end of protrusions 9 the faces defining the depressions are brought relatively closely together as will be apparent by reference to parts 10. The gap defined by two adjacent portions 10 is preferably such that its side walls are parallel and they extend for substantially one third of the radial distance of protrusions 9.

As an example, the protrusions 9 may be substantially spaced .005 inch from the edges of vanes 3 and the deepest portion of the opening may be .050 inch from these edges. It will be apparent then that when the portions 7 are positioned so as substantially to coincide with an extension of the vanes this element will produce a minimum capacitive coupling between the inner edges of the vanes 3 and the opening 3 will present a maximum inductive effect on the resonators. Rotation of the elements 7 through one half the angle defined by two adjacent vanes will position portions 10 substantially over adjacent vane tips near the cathode, producing the maximum capacitive reaction mum tuning range is achieved without introducing any extraneous attenuations other than those whiehwouldnormally be present in the fixed tuned magnetron due tothe spacing in the ends of'the pill-box. a v

'It will'be evident that when the protrusions 9 are substantially eoinciden-t with the vanes the resonators are partially shielded one from the other and there may not exist sufficientcoupling to produce the desired oscillating conditions. Accordingly, there may be provided slots or openings 11 in'each of protrusions 9' to permit desired intercoupling Preferably these openings are made intermediate the ends: of the resonator vanes so as to have the least effect on the. capacitive and inductive characteristics of the resonators, 4

As shown in Figs. 5 and 2; rotations of portions 1 and 7 may be accomplishedby'mounting. the entire pole piece assembly with suitablehall bearings, diagrammatically illustrated at 12 in Fig. 1, together with suitable external means 13, for adjusting the rotary position of this entire assembly. V

Means 13 may comprise an extension rod 14 fastened to a tuning assembly. A threaded rod 15 is journaled at one end around arod 14 and threadedly engaged in supporting member 16 fastened to thebody of the magnetron. A knurled knob 17 may' be provided for operating rod 15. A flexible Sylphon bellows, arrangement 18 is fastened to one part of rod 15 to' preserve the vacuum within the'magn'etron. i

It will be clear, however, that if desired the rotary element may be'made as aflseparatev plate substantially in contact with the lower portion of the pole piece assembly, this plate being made rotatable While the pole piece itself is retained relatively fixed.

Such an arrangement is shown by way of example in Fig. 3. In this figure pole piece 5 is shown fastened to copper covering 6, tuning elements 7 are rotatably mounted with respect to pole pieces 5 and copper covering 6, and may be supplied with ball bearings 19 and 20 to facilitate rotary adjustment-thereof. An extension rod 7 21 maybe fastened directly to tuning elements 7 and adjusted in a similar manner by a structure similar to that shown in Fig. 2.. a

While" the invention has been described showing th tuning element as a'solid piece it is clear that the eonstruction can be accomplished by using a ring with extended vanes to build up portion 7, there being fastened spade-like elements corresponding to 10 at the inner ends of its radial vanes. An annulardis plate may be fitted over the ring and vane assembly to complete the tuner.

Since the'tuning element substantially shields the pole V 7 piece parts of the magnetron this tuning element need not be made so as to fill in completely the volume between the inner ends of the pole piece and the inner surface of this tuning element. a

WhileiI have described above the principles of my invention in connection with specific apparatus, it is to be clearly 'understood'that this description is made only by way of example and not as a limitation to the scope of my invention as set forth in the objects thereof and in the accompanying claims. f V e -What is claimed is: V

1. A tunable magnetron comprising a plurality of cavity resonators each having regions of predominantly capacitive reactance, and regions of predominantly in- 4 said portions relative to said resonators to vary its tuning.

2. A tunable magnetron of the type comprising a plurality of successively adjacent cavity resonators open at one end and having resonator wall and partition portions adjacent partition portions providing predominantly capacitive reactance at the ends remote from the wall portions, and movable conductivemeans spaced above said open end for tuning said resonators, characterized in that said movable means is shaped to have parts closely adjacent the open end ofsaid resonator, and other parts more widely spaced from. said open end, and by means for shifting said movable means to move said closely spaced parts relative to said partitionportions of said resonators While maintaining said spacings substantially constant, to adjust said capacitive reactance.

3. A magnetron according to claim 2, wherein said resonators are positioned to form a substantially open ended yl e id mo able means eing, rotatably mounted at an end of said cylinder.

4. A magnetron according to claim 3, further comprising a rotatable pole piece mounted adjacent "said open end, said movable meansbeing rigidly fastened, to

said pole piece.

5. A magnetron according to claim 4, wherein similar tuning .means are mounted. at both open ends of said cylinder.

6. A magnetron comprising a cylindrical wall, a plurality of radially extending partitions fastened tosaid wall and extending inwardly thereof to. provide a series of 7 adjacent cavity resonators, the inner ends ofsaid parti-.

tions forming capaoitively reactive pick-up gaps in said magnetron, a cylindrical conductive member having a diameter slightly less than. the internal diameter of said cylindrical wallp'ositioned in fixed spaced relation to the.

radially extending edges of said. partitions, said member having closely spaced portions with respect to said edges' and other portions spaced a grea er distance from said edges, and said closely'spaced portions formed as radial protrusions from a ring on the outer edge of said member extending radially inwardly of a width substantially co: extensive with the. thickness of said partitions and terminated adjacent their inner ends witha portion of substam tially the dimensions of the space defined between adjacent partitions, whereby said element presents to said resonators a surface closely spaced with respect to said partitions substantially coincident therewith and other spaced surfaces substantially coincident with the open end contour of the cavities of said resonators in one position a forming capacitively reactive pick-up gaps in said magne tron, a cylindrical conductive member having a diameter slightly less than the internal diameter of said cylindrical wall positioned in fixed spaced relation to the radially extending edges of said partitions, said member having closely spaced portions spaced at distance in the order of .005 inch from said edges and othersportions spaced a distance in the order of .05 inch from said edges, and said closely spaced portions formed as radial protrusions from a ring on the outer edge of said member extending radially inwardly of a width substantially coextensive with the thickness of said partitions and terminated adjacent 7 their inner ends with a portion of substantially the. di.

mensions of the space defined between adjacent partitions, whereby said element presents to said resonators a surface. closely spaced with respect to said partitions substantially coincident therewith and other spaced surfaces substantially coincident with the open end contour of the cavities of said resonators in one position of said member, in Which the capacitive reactance is a minimum, and means for rotatably movable said member to increase the capacitive reactance, said capacitive reactance being a minimum When said protrusions are positioned substantially as bisectors of said cavities.

9. A tunable magnetron comprising a plurality of cavity resonators positioned in a substantially cylindrical array, each cavity having regions of predominantly capacitive reactance and regions of predominantly inductive reactance, and means externally of said resonators for tuning said magnetron characterised in that said tuning means comprises an element rotatably mounted coaxially of said cylindrical array and having portions predominantly eifective in said capacitively reactive regions of said resonators and other portions predominantly effective in said inductively reactive regions of said resonators, and means for rotating said element at substantially constant spacing relative to said resonators to shift said portions relative to said resonators to vary its tuning.

10. A tunable magnetron comprising a plurality of cavity resonators arranged in a substantially cylindrical array, each resonator having regions of predominantly capacitive reactance and regions of predominantly inductive reactance, and means externally of said resonators for tuning said magnetron characterised in that said tuning means comprises an element rotatably mounted substantially coaxial of said resonator array and having portions closely adjacent said resonators and portions more widely spaced from said resonators predominantly effective in said capacitively reactive regions and said inductively reactive regions, respectively, of said resonators, the surface pattern defined by said portions corresponding substantially to the pattern formed by said resonators, and means for rotating said element at substantially constant spacing relative to said resonators to shift said portions relative to said resonators to vary its tuning.

References Cited in the file of this patent UNITED STATES PATENTS 2,481,171 Spencer Sept. 6, 1949 2,506,955 Fracassi May 9, 1950 2,606,307 Pease et a1. Aug. 5, 1952 2,639,406 Crawford May 19, 1953 

